The most familiar type of Venetian blind window covering comprises a series of rigid slats or vanes suspended and controlled by a ladder cord system. The slats are typically wood, plastic or metal, and rest on the ladder cord rungs. The rungs are secured to front and rear vertical cords whose upper ends are secured to circumferentially spaced locations on a wheel. Limited rotation of the wheel, by means of a control wand or cords, causes relative motion between the front and rear cords, which in turn tilts the rungs and vanes. The entire array can be raised and lowered by additional cords which act to lift a bottom rail.
A modified type of Venetian blind is disclosed in U.S. Pat. No. 3,384,519 to Froget. There, the ladder cord system is replaced by front and rear cloth panels to which the vanes are heat welded. Preferably, the cloth panels and vanes are all made of thermoplastic yarns, to facilitate bonding by heat welding. Partial rotation of an upper drum, to which the panels are connected, shifts the panels relative to each other, thereby causing the vanes to tilt for light control.
Several more recent patents are directed to modifications of Froget's basic idea, wherein the vanes are made of flexible fabric, adhesively bonded to the front and back panels. Additionally, the entire array can be retracted from the window opening by winding it onto an upper wind-up roller by means of cords which lift a bottom rail. Representative of these patents are U.S. Pat. Nos. 5,287,908, 5,313,999, 5,320,154, 5,394,922 and 5,456,304, all assigned to Hunter Douglas, Inc., and a patent to Ren Judkins U.S. Pat. No. 5,339,882.
U.S. Pat. No. 5,664,613 (and subsequently assigned to a company owned by the assignee of the present application) describes another form of construction for a fabric Venetian blind. A continuous panel of relatively translucent material forms one facing of the blind. To that panel is bonded a series of parallel fabric strips at uniform intervals. Each strip comprises two adjacent portions of dissimilar material, one being relatively translucent and the other relatively opaque. The free edge of the opaque portion is bonded to the facing panel, while the free edge of the translucent portion is bonded to the adjacent strip at the junction line of that strip's two portions. The assembled translucent portions of the constituent strips become the second facing panel of the completed blind. That is, the second facing panel, rather than being a single continuous panel of fabric, is a composite of several parallel strips, each having a height dimension approximately equal to the width (or depth) of the vanes.
U.S. Pat. Nos. 5,490,553 and 5,603,369, assigned to Hunter Douglas, disclose in FIGS. 16-19 a vertical blind wherein each vertical blind vane is formed of the same strip of material as an adjoining portion of a facing panel on one side of the vanes. The single facing is a composite of narrow vertical strips. The vane portion of this strip is doubled back on itself. Another patent assigned to Hunter Douglas, U.S. Pat. No. 5,638,880, discloses in FIG. 26 a vertical blind wherein the facing on one side of the vanes comprises a series of vertical strips of material, each joined along one vertical edge to an adjacent strip, and at the other vertical edge to both the adjacent facing strip on that side and a discrete piece of substantially rigid, planar material forming the vane. The patent further discloses that both a front and a rear facing may be fabricated of such strips, and the strips and vanes can be oriented in either the vertical or horizontal directions.
U.S. Pat. No. 4,631,217, also assigned to Hunter Douglas, discloses in FIG. 2 a honeycomb or cellular type of window covering wherein a series of pleated, generally Z-shaped strips, each formed of a single piece of fabric, are bonded together in a manner whereby each strip forms the front portion of one cell, the rear portion of an adjacent cell, and a dividing wall between the two cells. The dividing walls, however, are incapable of functioning as the vanes of a Venetian blind type of product, because they remain substantially perpendicular to the front and rear faces of the window covering throughout the full range of expansion and collapse of the cells.
Known processes for manufacturing these prior art fabric Venetian blinds are complex, slow and costly, and have contributed to a high price for these otherwise attractive products.
Accordingly, it is a principal object of the present invention to develop a simplified and more economical method for manufacturing fabric type Venetian blinds, using smaller and less costly equipment, allowing fully continuous processing, and resulting in a more uniform and high quality finished product.